Corrosion is an extremely broad problem and encompasses, but is not limited to the following categories of industrial materials: structural and manufacturing applications, aqueous system applications, coatings and films, lubricant, fuel and hydraulic fluid additives, natural gas and oil industry applications and metal treating baths.
In particular, the problem of corrosion of metal surfaces in contact with various corrosive environments such as gas, electrolyte solutions and solvents is long well known. It is quite an expensive proposition. According to a 1978 National Bureau of Standards Special Publication, corrosion of metal surfaces cost the economy in excess of $70 billion a year, about 4% of the gross national product.
Currently, there are various types of products available to protect metallic surfaces. Popular systems include inorganic pigments (inhibitive and sacrificial) and barrier coatings. The inorganic pigment products enjoy a lion's share of the market. In the inhibitor pigment market, 75% consists of chromate pigments, which are considered to be toxic and the effluent waste problems are of concern.
Currently, the pigments which have been developed to replace chromate, barium and lead based pigments themselves lack the efficacy of corrosion prevention that the toxic pigments possess. Therefore, the need exists for a corrosion inhibitor which is relatively non-toxic, has a high degree of efficacy and is cost competitive. Moreover, such corrosion inhibitor should have limited water solubility, thereby extending the protection of metal surfaces for a longer period of time.
Accordingly, an object of this invention is to provide compositions which are low toxicity inhibitors capable of replacing chromate and other toxic pigments.
Another object of this invention is to provide compositions which can be applied to surfaces to inhibit corrosion and pitting of the metal.
Another object of this invention is to provide corrosion inhibiting compositions which are insoluble in water, thereby increasing the protection period of the metal surfaces.
Another object of this invention is to provide corrosion inhibiting compositions which are liquid in form, thus easy to handle and incorporate into paint formulations. The distribution of such composition in the paint system is also greatly enhanced.
Another object of this invention is to provide corrosion inhibiting compositions which consist of both anodic passifier groups, such as zinc and calcium, and cathodic passifier groups, such as substituted amines.
Another object of this invention is to provide corrosion inhibiting compositions which are substantially more effective than the currently used inhibitive pigments.